At this point, following Openpilot’s driving model releases feels less like keeping up with autonomy research and more like binge-watching a Netflix series that never stops dropping new episodes. Testers are swapping models mid-drive just to keep up, joking about needing a family tree UI to track the mess, and treating every new release like a lottery ticket that might finally deliver the perfect blend of lateral and long. Blink once, and you’re already behind. Sleep? Forget it.
August 2025 crystallized this chaos better than any month in recent memory. In just over a week, we saw a torrent of models hit the wild, tested, debated, and sometimes abandoned before the ink was dry on their changelogs.
Below, we break down each release — what it promised, how it performed, and how the community received it.
Chapter List
- Steam Powered Model (Aug 15)
- Watermelon Model (Aug 16)
- Green Watermelon (Aug 16)
- Kumar’s Vibe (Aug 16)
- Green Watermelon v2 (Aug 17)
- Green Watermelon v3 (Aug 22)
Steam Powered Model (August 15, 2025)
The Steam Powered model (SP) marked the start of the frenzy. As part of the Simple Plan series, it introduced refactors to the modeld action head designed to smooth lateral performance and improve stop sign handling.
Lateral: Stable and predictable on highways, with smoother steering and fewer notches than earlier SP builds. It managed both 90-degree turns and poorly marked roads with surprising confidence, though some users still saw a left-lane hugging tendency.
Longitudinal: Stopping for stop signs was a standout improvement. Highway following was smooth and natural, though a few testers reported random braking or jerky acceleration in heavy traffic. Overall smoother than TR6 or UV.
Edge Cases: Some reports of following leads into exits, mixed rain performance, and occasional gas-gating issues depending on settings.
Reception: Widely praised as one of the most balanced models of the cycle, with many testers adopting it as their daily driver. Its stability was underscored by being merged into Openpilot’s main branch soon after release.
The Watermelon Model (August 16, 2025)
The next morning brought the Watermelon model (WM) — a build with a lighthearted name but serious ambitions for highway lateral refinement.
Lateral: Much smoother at high speeds, with reports of confidence even at 75 mph. But sharp turns exposed weaknesses: some testers experienced oversteer that pushed the car toward curbs. A “floaty” feel compared to UV but generally more composed.
Longitudinal: Strong highway stability, though quirky in city driving. Notably, it developed a reputation for “California stopping” — hesitating at stop signs rather than committing to a full halt.
Edge Cases: Sometimes recalled the behavior of TR models, overshooting tight corners. Still, testers saw it as progress, particularly in highway cruising.
Reception: Cautious optimism. Many liked WM’s improvements, but before the day was done, a successor had already appeared — Green Watermelon.
The Green Watermelon Model (August 16, 2025)
Released only hours later, gWM refined Watermelon with tinygrad-based updates and a broad rollout.
Lateral: Mixed results. Some saw smoother steering, but others reported overturning followed by abrupt corrections, hugging parked cars, and in severe cases, confident curb strikes that forced takeovers.
Longitudinal: Smooth highway behavior, but stop sign compliance remained unreliable. Testers also noted it lacked “scooching” around semis, reducing comfort in mixed traffic.
Edge Cases: Better rain handling than most models, but poor nighttime performance — including mistaking the road entirely.
Reception: Generally negative compared to Watermelon. The improved rain performance wasn’t enough to offset dangerous curb-hugging. Many testers skipped it after early reports of unsafe turns.
Kumar’s Vibe (August 16, 2025)
Capping off the day, Kumar’s Vibe was a custom merge model blending DTR6, WM, and gWM policies atop the SL3v2 Vision backbone.
Lateral: Smooth centering and unwinding after turns impressed early testers, but a tendency to hug the inside of curves sometimes forced interventions.
Longitudinal: Widely considered the smoothest braking and acceleration of any model so far, praised for intersection handling and consistent highway following. Some felt it was too conservative in spacing, occasionally compressing distances unsafely before correcting.
Edge Cases: Better object avoidance than many peers, but occasionally misread lanes or even aimed for guardrails.
Reception: Excitement around its smoothness was tempered by safety concerns in curve handling. Some daily-drove it, but the consensus was that while it excelled in comfort, it wasn’t yet reliable enough across scenarios.
Green Watermelon v2 (August 17, 2025)
Released as a fast follow-up, gWM v2 tried to fix its predecessor’s flaws.
Lateral: Felt more planted and stable, with smoother steering recoil after turns. But lane bias issues persisted — hugging either left (toward oncoming traffic) or right (toward cones/parked cars).
Longitudinal: Strong highway behavior and smooth integration with DEC, but braking at intersections was often too late. Users also reported sluggish takeoffs after leads moved.
Edge Cases: Lane changes were smooth, but the model sometimes followed leads into exits. City braking remained inconsistent.
Reception: Mixed but better than gWM. Some testers daily-drove it for highway use, but the hugging and city issues limited its appeal.
Green Watermelon v3 (August 22, 2025)
The third iteration, gWM v3, was billed as the most refined version yet.
Lateral: On highways, it was stable, ping-pong-free, and smooth through curves. But city driving exposed flaws: lazy turning, frequent left-bias, and a tendency to cross lines or cut corners. In DEC mode, some users saw dangerous lane switches into turn lanes.
Longitudinal: Smooth, human-like throttle control and improved braking over DTR6. Still, stop-and-go traffic exposed hesitations in acceleration and overly aggressive braking. Stop sign and light handling was inconsistent without a lead vehicle.
Edge Cases: Strong on highways and roundabouts when tuned, but failed badly in city roundabouts for others. Lane changes were smooth, though the model sometimes followed leads into exits.
Reception: For highway-focused testers, this was the best model of the week. For city drivers, it was one of the worst. The split verdict solidified gWM v3 as a highway specialist rather than an all-arounder.
Summary Table
| Model | Release Date | Strengths | Weaknesses | Reception |
|---|---|---|---|---|
| Steam Powered | Aug 15 | Stable highway lateral, strong stop sign handling, balanced overall | Occasional random braking, mild left bias, rain inconsistent | Widely praised, merged to main branch |
| Watermelon | Aug 16 | Smooth highway lateral, better than UV | Oversteer in sharp turns, “California stops” | Cautious optimism, quickly replaced |
| Green Watermelon | Aug 16 | Smooth highway, improved rain handling | Dangerous curb strikes, poor night driving | Generally negative |
| Kumar’s Vibe | Aug 16 | Exceptional long, smooth braking/accel, good unwinding | Unsafe in curves, occasional lane errors | Excitement but ultimately unreliable |
| Green Watermelon v2 | Aug 17 | Planted feel, smooth highway in DEC | Persistent hugging bias, weak city braking | Mixed, better than gWM but not fully trusted |
| Green Watermelon v3 | Aug 22 | Excellent highway stability, smooth throttle, improved braking | Lazy turns in city, line crossing, weak stop/go | Highway favorite, poor for city use |